Volume control



March 2, 1948. E, Q LODGE 2,437,166

VOLUME CONTROL 4 Sheets-Sheet 1 Filed June 2, 1944 50m/N0 6, om-E ATTOR EVS March 2, 1948. E. G. LODGE 2,437,166

- VOLUME CONTROL Filed June 2, 1944 4 Sheets-*Sheet 2 INVEN'roR '/fa/va G. 0065 March 2, 1948. E. G. LODGE VOLUME CONTROL Filed June 2, 1944 4 Sheets-Sheet I5 @l/@zgig March 2, 1948. E. G. LODGE 2,437,166

VOLUME CONTROL Patented Man'. 1 948 VOLUME CONTROL Edmund G. Lodge, Rosemont, Pa., assignor to International Resistance Company, Philadelphia, Pa., a corporation of Delaware Application June 2, 1944, Serial No. 538,389

(Cl. 20L-55) y 8 Claims. 1

This invention relates to a rheostat or the like particularly suited for volume and tone control 'Y in radio and a method of making the same.

One of the objects of this invention is to provide a volume control structure which will be simple, practical and thoroughly durable. Another object is to provide a method of producing such a volume control wherein the usual number of assembly operations is'materially reduced. Anotherv Objectis to provide a method of producing such a volume control in which important economies are achieved by a reduction in number oi parts and the expense of such parts. Another object is to provide such a method of producingp a volume controlwhereinthe resultant costs of manufacture are materially reduced. Another object is to provide such a volume control and method wherein a unitary structure comprising a major portion 0f the control is produced in a single quick operation. Another object is to provide for use of elements in such an operation which have been previously completed with all desired resistance characteristics. Another object is to provide such a control and method in which the electrical connection between the ter-l minals and resistance element is reliable and of highest quality. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements,

' arrangements of parts and in the several steps and relation and order of each of the same to one or more of the others, all as will be illustratively described herein, and the scope of the application ofv which will be indicated in the following claims.

1n the accompanying drawings in which is shown one of the various possible embodiments of this invention:

Figure 1 is a top plan view of the volume Acontrol with the cover removed;

Figure 2 is a sectional view taken along the'\ line 2-2 of Figure 1 on a slightly enlarged scale and with the cover assembled on the unit;

Figure 3 is a fragmentary sectional view taken along the line 3-3 oi Figure 1;

Figure 4 is an exploded perspective of vcertain parts of the control before the major assembly operation; f

Figure 5 is a fragmentary plan view of the upper section of a mold used. during such assembly operation;

Figure 10 is an exploded perspective similar to l Figure 4 but showing another embodiment of the invention.

Similar reference characters refer to similar parts throughout .the several views of the drawings.

Referring to Figures 1 and 2, the volume control comprises generally a base assembly generally indicated at I0, including a resistance element Il, an operating shaft I2, and an armature part I3 secured to the shaft and contacting the elef ment.

Base assembly ID is a unitary structure in which the various individual parts have been molded into a unit in a manner to be later described. It includes the central bushing I4 having an enlarged threaded neck portion Ma for reception ofthe shaft I2 and an annular shoulder portion I4b. Bushing I4 also includes an annular flange part Mc and extending therefrom is a sleeve portion I4d through which the reduced portion I2ct of the shaft I2 extends. A molded base I5 which is a part of the base yassembly I0 and which is preferably a plastic having dielectric properties, such as phenolic condensation product, rests on the lower side of the iiange portion I4c and extends. outwardly therefrom as viewed in Figure 2. Base portion I5 also includes a` portion I5a fitting snugly about sleeve portion Idd.

Preferably there is an annular groove Ile in sleeve portion Md and the material of the base I5 is molded to lill this groove.

The resistance element II which is shown as a separate Dart in Figure 4 before the molding operation comprises a circular, fibrous strip having a resistance coating IIa applied thereto and highly conductive coatings IIb and IIc covering and enveloping all sides of the opposite ends thereof. The resistance coating IIa is preferably a graphite or carbon deposition in a plastic binder such as .any well-known varnish. This coating may be applied by spraying, dipping, or other vmethods and a variety of final resistance characteristics, such as complex tapers and gradients, may be given the resistance element in accordance with well-known accepted practice.

lol

The coatingsll Ib and llc are preferably metallic, i

such as silver, and applied by spraying, painting, sputtering or other methods.y

Referring back Lto Figures 1 and 2, element J insulating ring 2S is disposed within the casing 23 adjacent the side wall thereof.

Accordingly, there is provided a volume control which is simple in construction and operates with ease. Furthermore, lt will be noted that the main portion of this volume control) comprises the base assembly iii. The other parts of the control may be easily tted into position on the base assembly thus making for a rapid completion of the control once the base assembly is provided. An important aspect of this invention is the provision of a rapid and ecient method of manufacturing these base ass i blies.

i i is partially sunk in the base I5 during the molding operation so that a binding connection, such as a bond, is formed between base and element. The element is thus positioned in the base with its end portions adjacent the opposite sides of a central terminal I6, as best seen in Figure 1.

Central terminal I6 and\side terminals i I and I8 all have portions embedded inthe base I5 during the molding operation and portions extending radially from the base for easy electrical connection. Thus terminal I6 includes an embedded portion Ilia with a hole IGb and a protruding portion I6c. A pimple I 6d is provided inl terminal I6 adjacent the periphery of base I5, for pur-v i poses of electrical connection, as will be later fully explained. The structure and assembly of terminals II and I8 and adjacent portions of the base ore particularly, this method comprises a molding operation involving the parts shown in Figure l comprising the bushing It, the element il, the terminals it, il, and It and two sheets 2l and 2@ of resin-impregnated fibrous material which may be uncured or partially cured. The surface of sleeve portion Idd of the bushing adjacent annular groove ileis knurled and slightly larger in diameter than holes 21a and 28a provided in the sheets ai and ze. The resistant-,e

element il is prefabricated in the manner described above so that it is provided with the proper and desired resistance characteristics. The parts `lare then ready for the molding operation `and they are molded in the relation indicated by ex- I5 are identical and thus the'following descrip- 1 tion is limited to terminal I8. As best shown in Figure 3, terminal I8 comprises an embedded portionl I8ay and a portion'J IBb extending there-A sleeve portion Idd of the bushing while a stop arm 2| is secured below the collar as viewed'in Figure 2, for example, by heading over the end of the shaft. Stop arm 2l may cooperate with a stop 22 diagrammatically indicated in the drawings and so located on the cup-shaped casing 23 as to stop rotation of the armature arm as its contacting brush portions reach points adjacent the ends of the element.

The 4armature arm I3 is preferably substa tially triangular in shape and includestwo cute out brush portions I3a and I3b which are bentl downwardly to engage the adjacent surface of the resistance element. The brush DOrtions are preferably resilient in character to maintain a. close ploded perspective in Figure 4.

' To be specific, sheet 2l is slipped down upon sleeve portion Ilid of the bushing until it rests flat against the ange portion I Gc thereof. 'Ihe sheetn28 is similarly related to the bushing and f the left-.hand portion of the terminal It, as viewed in Figure 4,- is slipped between the sheets 2l and 2d. The element il rests against thel sheet 28 with the inwardly-extending portions of terminals il and i8 resting beneath the coatings iIb andi lic thereon. This is the position ofpartsshowninFigures'Zand 8. f

The parts shown in Figure 4 may be molded into the base assembly I0 by any of several well-known methods, all depending upon 'particular manufacturing conditions. Thus an upper mold section 29 (Figure v5) and a lower mold section 30 (Figure 6) may be utilized having cavf ities 29a and 36a shaped to provide the desired running contact with the element at all positions of the armature arm. A lcoil wire connector' 24 has one erid supported by a lanced portion I3c of the armature arm and connected to the arm iSd on terminal I6; such connections may be achieved by welding or other well-known manner. .f I

A ground plate 25 iii@ over ange portion Mc of the bushing and extends outwardly to rest on the base I5. Plate 25 is held in position bya suitable number of ear portions 23a ot the casat i3d; the other end is connected to the pimplev form of base assembly suitable for a particular volume control construction. It will be understood that such a base assembly is a basic part of any volume control, and thus this methodwis not'limted to a particular construction, such as the volume control structure hereinabove described. However, where such base assembly is to be used in the above volume control, cavities 29a and 30al will take the shape indicated.'

Immediately prior tothe actual molding operation, i. e., before pressure and heat are applied to the parts and the top and bottom sections of the mold -brought together, the parts of the base assembly and the mold sections will have thel -positlons shown in Figures 7 and 8. In addition to the upper and lower mold sections 29 and 30, there is a plunger 3i extending into the sleeve portion Idd of the bushing and supporting the bushing and related parts in relation to the lower mold 30. Upon the application of heat and pressure, the sheets 21 and 28 are reduced to a plastic state and merge with each other' to become the I1, and I8 and the element Ii -assume the posiy tions descrlbedgabove and shownin Figures 1 and 2, and thus when the mold sections are sepaj rated, the base assembly is complete. `Element ing 23 bent down thereon during assembly. A1115 -Il is firmly embedded in and bonded to the base unitary and integral base I5.v The terminals I6,

Y essaies e ig is. A11 c" the terminan are embedded in the base with the terminals I1 and i8 in electrical contact with the conductive coatings IIb and I Ic ci the element. The resistance coating Ila on the element ii is baked thereon' prior to this molding operation at a temperature in the neighborhood of 200 C. The above molding operation may be successfully carried on at temperatures in a range of 150 to 160 C., materially below the baking temperature of the element. Thus it has been found in practice that this molding operation has practically no eilect on the resistance characteristics of the element. The most the molding operation might do would be to lower the resistance value of the element. Hence, allowance for any such changes in resistance value can be predetermined and taken care of in adfvance. The molding operation will not vary any complex tapers applied to the resistance element prior thereto.

In the embodiment of the invention shown in Figures 9 and l0, the various parts are preferably identical with those described above and related in the same manner except for the additioncf a plate 35 embedded in the base I5. This plate 35, formed from a good heat conducting metal such as copper, preferably takes the vshape best seen in Figure 10. Thusthere 'is a substantially circular central portion' 35a and radially extending leg portions'35b, 35o, 35d and 35e. The legs 35h and 35e border a V-shaped opening terminating in a central aperture 35i. v

The base assembly may be molded ina single i molding operation such as described above, the

parts being related in the mold in the relative positions shown in Figure 10. Thus after the extending radially fromthe base i5. The legs are then bent back over the top portion of the base as viewed in Figure 9, and after final assembly of the parts the ground plate 25 rests on the legs and on lange part Mc of the bushing.

In operation the resistance element heats the base I5, but this heat is distributed throughout the base by the plate to avoid hot spots at any particular point. Furthermore, plate 35 aids in the rapid dissipation of heat so generated by conducting the heat to thek ground plate 25 which is connected to the bushing I4 and the cover plate 23 which are exposed to the atmosphere.

Accordingly, by this method a construction is f baking the strip to provide a resistance elementl achieved wholly lacking in rivets, eyelets, or like of the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, itis to be understood that all matter hereinbefore set forth or shown in the `accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim: l

1. In the art of assembling a volume control part including a base of insulating plastic. a cenb trai bushing, terminals, and a resistance element comprising an insulating core coated with resistance material, the steps comprising completing the resistance element with the desired resistance characteristics and form to be used in the volume control when completed. relating the parts with terminals in electrical contact with spaced points on the element, and moldingthe plastic about the parts to provide s base with the completed element bonded to one side thereof and with portions of the terminals embedded in the base and in contact with said element.

2. In the art of assembling ai volume control part including a base of insulating plastic, a central bushing, terminals, and a resistance element comprising aninsulating core coated with resistance material. the steps comprising completing a resistance element haying desired resistance characteristics and form to be used in the volume control when completed, and molding a base and terminals in position so that the' element is bonded to the base and the terminals are electrically connected to the element at spaced points.

3. The method of assembling a resistance element and the base of a volume control, comprising the steps of coating a dielectric strip and baking the strip to provide a resistance element having proper characteristics, and heat molding the preformed element upon a plastic base portion to form a bond therebetween without varying materially the resistance characteristics of the element.

.4. The method of assembling a resistance element and the base of a volume control, comprising the steps of coating a dielectric strip and having proper characteristics, and heat molding the'preformed element upon a plastic 'base portion, the molding temperature being below the baking temperature to form a .bond therebetween without varying materially the resistance characteristics of the element. 5. The method of assembling a volume control base with its resistance element, comprlsingpreforming the resistance element withI the desired characteristics by baking, relating the element with a sheet of resin-impregnated lbrous material which has not been completely cured, and applying heat and pressure to the sheet and element to mold them together to form a bond therebetween Without varying materially the resistance characteristics of the element.

6. The method of assembling a volume control base with its resistance element, comprising preforming the resistance element with the desiredy 'the element to a plastic base to form a bond therebetween, said molding operation being at a temperature sumciently low to avoid varying materially the resistance characteristics ol' the element.

8. Ihe method of assembling a resistance element and the -base of a volume control, comprising the steps oi heating a strip at a temperature m the neighmrha otono' c. :o form a resistance element having the proper haracteri STATES ,PATENTS istics and heatmolding the element to a plastic v Number v .Ngmg Date base at a. temperature in the neighborhood of 1,985,166 Haroldson Dec.. 18, 1934 150 C. to form a bond between the element and 5 2,282,328 Herrick et al. May 12, 1942 the base without varying materially the resistance 1,745,400 Brennecke Feb. 4. 1930 characteristics of the element. 11,871,492 Brennecke A118. 16, 1932 l EDMUND G. 1,913,473 Brennecke June 13, 1933- Y 2,163,798 Mucher June 27, 1939 REFERENCES cl'nm ,10 2,269,136 'reukamp Jan. s, 1942 The following reference# are of recon-1in the l file of this patent: v 1 

